The fight that was happening earlier in chat, was in parts about the significance of the difference between open source and free software. So what's about that?
Practical view: Looking at it from an practical angle, the differences are insignificant. Most licenses that are free software are also open source and most open source licenses are also free software. If it happens to be not the case for one or another, that are mostly edge cases. Also the both movements more or less share the same goal: more rights for the users of software. So from a practical point of view, the differences between the two terms are not important.
Philosophical view: In this question I asked about the philosophical differences between the two terms. The answers involve different things. Both camps point at differences in philosophies. From this point of view the differences are important.
If you think the differences are insignificant or important strongly depends on which side you focus more, which point of view is more important. So overall: It is an opinion!
Therefore claiming the other side acts irrational, is a sect, misses the point, is deviating from the right path and so on can be offensive. So, if you think the difference is not important, please don't think of the ones who think different as overzealous nutjobs, but just as people who have a different opinion. After all Eric S. Raymond, Bruce Perens and Tim O’Reilly thought the difference was important as they coined the term Open Source although Free Software already existed, otherwise their move would have been very redundant. If you think the difference is important, please don't see the ones who don't think so as naive children, who haven't thought the implications through. Both sides have their rationale, which reasoning is more important for you is clearly a matter of opinion, please handle it so.